The present invention is directed to manufacture of glassware, and more particularly to a method and apparatus for testing so-called dual-stage blowheads used in the final-blow operation of a glassware manufacturing machine. A second aspect of the invention relates to use of this method and apparatus for testing plunger coolers used in an initial parison-forming operation of a glassware manufacturing machine.
Glassware, such as glass bottles, is typically made in a so-called individual section machine, which includes a plurality of identical sections that operate out of phase with each other to produce glassware. Each section includes one or more blank molds, in which gobs of molten glass are either pressed or blown to form parisons. Each parison is then removed from the blank mold and placed in a final-blow mold. A blowhead is lowered over the parison in the blow mold, and final-blow air is directed into the parison through the blowhead to form the parison against the internal surface of the final-blow mold.
Conventional blowheads include an air passage for feeding final blow air from an inlet to the inside of the parison. One or more second passages branch from the first passage for feeding air around the outside of the finish of the container in the blow mold to cool the finish and support the finish against outward expansion during the blowing operation. It is desirable to test such blowheads for obstruction of the final blow air passage, or obstruction of one or more of the finish air cooling passages, and apparatus has been proposed for this purpose. In such apparatus, test air is fed through a pressure regulator and a flow meter to the single inlet of the blowhead, and air pressure and flow are monitored. Reduced air flow may indicate obstruction of one or more of the air passages, potentially calling for redrilling of the air passages or replacement of the blowhead.
Blowheads of the described character have the drawback that the ratio of final blow air to finish cooling air is determined by the ratio of the diameters of the air passages in the blowhead, as well as other fixed factors. Since the finish cooling air passages branch from the final air passage within the blowhead, it is not possible to vary the ratio of finish cooling air to final blow air. It has therefore been proposed to provide a so-called dual-stage blowhead, also sometimes called an isolated finish cooled blowhead, in which the finish cooling air passages are separate from the final blow air passage and are provided with a separate inlet on the blowhead. Thus, the ratio of final blow air to finish cooling air can be controlled and varied by feeding air at different flow rates and pressures to the final blow and finish cooling inlets of the blowhead. However, a limitation on use of such dual-stage blowheads lies in the fact that such blowheads cannot be tested employing the conventional blowhead test apparatus described above.
Individual section machines are conventionally provided as either blow-and-blow machines or press-and-blow machines. In blow-and-blow machines, a blowing operation is employed to form the parisons within the blank molds. In press-and-blow machines, a plunger is employed in association with each blank mold to form the parison by pressing the molten glass gob against the confines of the blank mold. Because of the high temperature associated with the molten glass in the blank mold, the plungers are conventionally internally cooled by feeding air through a plunger cooler against the internal surface of the plunger. Plunger coolers take many conventional forms, and generally comprise a hollow needle or cone with a multiplicity of openings for directing air under pressure against the internal surface of the plunger. Blockage of air holes in the plunger cooler can result in hot spots on the plunger and manufacture of unsatisfactory glassware. Furthermore, it is desirable for all plunger coolers and all plungers of each machine section, and of the entire IS machine, to possess the same operating characteristics for optimum uniform glassware manufacture. A second aspect of the present invention relates to testing of plunger coolers to determine whether the plunger cooler openings must be reworked or redrilled.
It is therefore a general object of the present invention to provide a method and apparatus for testing air flow capability of dual-stage blowheads that are clean in operation, that provide accurate and consistent results, and that indicate when redrill or rework is necessary to remove obstructions from the air passages, particularly the finish air cooling passages. Another object of the present invention is to provide a method and apparatus of the described character that can be readily modified for testing plunger coolers.
Apparatus for testing air flow through dual-stage blowhead in accordance with a presently preferred embodiment of the invention includes an adapter block with facility for releasably receiving a dual-stage blowhead. The block has a first block passage for feeding test air to a first inlet of the blowhead for conducting blow air to a parison, and a second block passage for feeding test air to a second inlet of the blowhead separate from the first inlet for conducting finish cooling air. Air is directed from an air source separately to the first and second block passages, and air flow is measured in each path. When air flow through the finish cooling air path is less than a predetermined threshold, or less than a predetermined ratio with respect to the final blow air, this may indicate a need to redrill or otherwise rework the finish cooling passages in the dual-stage blowhead.
A blowhead cup is replaceably mounted on the apparatus adapter block in the preferred embodiment of the invention for removably receiving the blowhead, and for providing air paths separately to the final blow and finish cooling air passages of the blowhead. The blowhead may be mounted to the blowhead cup by bayonet mounting means, or by any other conventional blowhead mounting technique. In the preferred embodiment of the invention, air pressure and mass air flow are measured separately for the final blow air and the finish cooling air fed to the blowhead under test. A test container is inserted into the blowhead for simulating back pressure of air at the blowhead passages during operation for blowing a container.
In accordance with a second aspect of the invention, one of the air flow passages, preferably the air flow passage for finish cooling air, is provided with a fitting and a removable plug. When it is desired to test a plunger cooler, the plug is removed and the plunger cooler is threaded into the fitting. The final blow air path is blocked, and air is fed to the plunger cooler, while pressure and mass air flow are monitored. Air flow less than a preselected level to the plunger cooler may indicate a need to redrill or otherwise rework the cooling air passages in the plunger cooler.
There are therefore provided by the invention a method and apparatus for testing air flow operability of dual-stage blowheads, and additionally plunger coolers in the preferred embodiment of the invention. The invention thus provides facility not only for testing absolute air flow capability of dual-stage blowheads and plunger coolers, but also the capability of matching air flow capabilities of the blowheads and plunger coolers in each section of an individual section machine. This, in turn, provides improved consistency of glassware produced.